Staybolt



Feb. 8, 1938. R. WA FRIDAY 2,107,604

sTAYBoLT original Filed oct. j4, 1932 2 sheets-sheet 1 Fig-4 'A Feb. 8, 1938.

Y R. w. FRIDAY STAYBOLT Original Filed Oct. 4, 1932 2 Sheets-Sheet 2 Patented Feb. 8, 1938 UNITED STATES PATENT OFFICE Application October 4, 1932, Serial No. 636,152 Renewed July 6, 1937 14 Claims.

t an improved method of testing boiler staybolts to determine their condition.

Another object of my invention is to provide a new and improved staybolt structure assembly.

If staybolts are broken it renders the boiler unsafe for use. It is, therefore, essential to have some means of determining the condition of the staybolt. At present, llexible staybolts are tested by one of two methods, either by removing the boiler jacket, lagging, and caps, and then applying the hammer test, or, in case hollow flexible bolts are used, the electric contact method is used to determine whether or not the tell-tale `hole is open all the way into the head. In case the hole in a bolt is not open all the way into the head, the hole is cleaned out and thereafter the boiler is put under hydro-static pressure to detect broken or badly fractured bolts by leakage of water or steam through the tell-tale hole of a fractured bolt into the iirebox. If sediment in a bolt is so hard that it covers the fracture so that the water cannot enter the tell-tale hole then the present method of testing will not indicate the real condition of the bolt.

In my invention the necessity of employing either of these methods of test is eliminated and the condition of the flexible staybolts is quickly and easily determined without any previous preparation of the boiler for the purpose of making the test. In testing a bolt according to my invention, I include the bolt in an electrical circuit which is broken or which has its resistance materially increased by a faulty condition of the bolt.

A bolt embodying my invention is provided with a longitudinal hole or bore extending throughout its length or extending at least from the firebox end of the bolt into the head of the bolt at its other end. In this hole I insert an insulated rod or core preferably of metal or alloy. The insulation on the outer surface of this rod prevents contact of the rod with the staybolt except within the head of the bolt where the rod is electrically bonded or connected to the bolt. The rod is therefore insulated electrically from the bolt shank or body throughout the entire length of the bolt body in which breakage may occur. In the bolt assembly structure, the head of the bolt is, in turn, insulated from the bOilel' Sheet by being provided either with an insulating layer disposed between the head proper and a bearing ring encircling the head, or by an insulating medium disposed between the head of the bolt and its seat in the sleeve or boiler plate. I have also practiced my invention by employing a sleeve which is provided with an annular bearing member which forms a seat for supportingthe head of the bolt, this annular bearing member being insulated electrically from the sleeve. 10

With an assembly such as I have described, an electric current may pass from the tip of the rod or core at the re sheet end of the bolt, along the core to the head of the bolt, thence back toward the re sheet by means of the bolt body itself, so l5 that a testing circuit may be completed through the bolt by contacting the tip of the bolt core and the sheet or the firebox end of the bolt by the terminals of a suitable testing circuit, including, for example, a low voltage battery connected in series 2O with an electric light or other current-responsive or voltage-responsive indicator.

If the bolt is sound, and such contact as above described is made, the light bulb or indicator will become energized, but, if the bolt is broken the 25 light bulb will not be illuminated or the indicator energized to any degree. I do not confine myself to this particular method of indicating the ow of electrical current, to indicate the condition of the bolt, since any resistence-measuring scheme 30 may be used, as desired.

In this way it may be ascertained whether or not the bolt is broken. This constitutes a simple and improved method for determining the condition of a flexible staybolt. 35

The novelty and basic difference of my invention from the present method is in the fact that the present method of electrically testing the hollow or tell-tale type of flexible staybolt only indicates whether the tell-tale hole is open through- 40 out the bolt into the headed end, but does not test the condition of the bolt, whereas my invention actually tests the bolt itself and indicates whether the bolt is broken.

Various modifications of the bolt and bolt 4,5 structure assembly are shown in the accompanying drawings, in which Figure 1 is a front elevational view of a bolt embodying the principles of this invention;

Figure 2 is a longitudinal sectional view of the bolt in Figure 1;

Figure 3 is a View, partially in section and partially in elevation, of a bolt assembly structure of one form embodying the principles of this invention, and illustrating how the bolt may be tested by a suitable contact device at the end of the individual bolt;

Figure 4 is a longitudinal sectional View of the bolt in Figure 2 in position in an assembly;

Figures 5 and 6 are longitudinal sectional views of modified bolt assembly; and

Figure 7 is a sectional view of the outer-sheet end of a further modification of a bolt structure.

As shown in Figures l and 2, a staybolt Ill, constructed in accordance with the principles lof my invention, embodies a cylindrical shank or body II and an enlarged head I2 integral therewith. The bolt body II has a central longitudinal passage or orifice I3 extending the length of the body of the bolt to a point I4 in the enlarged head.

In order to provide a freely available terminal to connect an external electric circuit to the end of the bolt body adjacent the head, I provide a rod or core I5 in the bolt passage I3 and join the inner end of the rod to the bolt in any suitable manner, such as by Welding, to provide a good electrical contact with the head end of the bolt body. The rod is electrically insulated from the bolt body along its length by a layer of any suitable insulation i 6, such as a non-conducting refractory or asbestos material.

In order to otherwise insulate the bolt from the structure in which it may be located, so that there may be no leakage of testing current through the structure and the adjoining, bolts, the head of 'the bolt is formed of two co-operating and closely fitting sections II and I8 insulated from each other to introduce a layer of insulation between the bolt head and body and the sheet at which the head will be disposed.

The upper section I'I of the head contains a recess I9 `such as slot or square hole for `driving the bolt and is integral with the body II. The lower section I8 of the head constitutes a cylinder shaped to t over the body or shank of the bolt along a part 2| of the longitudinal periphery of the bolt, and also shaped to rest against a shoulder 22 on the under side of the head section I'I. A Alayer of insulating material V23 is disposed between the two co-operating sections I'I and I8 to prevent current leakage between them.

The lower section I8 serves as a seat or bearing ring for the bolt head I'I to permit the bolt to re-adjust itself as may become necessary during operation.

The condition of the boltbody may` thus be tested easily by reason of the two ends or terminals of the bolt body .available for connection to an electric circuit, through the center rod I5 and the tip or threaded end 24 of the bolt body. For suchtesting purposes a simple circuit may be employed, as shown in Figure 3, containing a source of current 26, a meter, light bulb or other indicating device 21, and a two-point terminal plug 28. i.

. In Figure 3 is shown a bolt structure assembly comprising a modified form of bolt 3l having the saine center passage and core rod but .having a solidhead 32.Y The head 32 is seated on an insulating ring or bushing 33 which rests against a sleeve 34 that is to be secured to a sheet or The lower surface of the bolt head is curved where it engages the inner surface of the bearing ring 33 to permit the bolt head to adjust itself under the varying temperature conditions encountered in the boiler structure Vheld together by the bolts. The insulating layer 31 between the bearing ring 33 and the sleeve 34 prevents electrical Contact between the bearing ring and the sleeve, and thereby prevents current leakage from the head end of the bolt when the testing circuit is applied. The path of the testing current is thus confined to the center rod and the shank or body of the bolt. The resistance of a normal bolt will lie between certain values as predetermined by measurements of known normal bolts. A variation of resistance of a tested bolt from the range of average values will indicate a faulty bolt.

The central core rod should be joined to the bolt head at a point well into the head and beyond the vjuncture of the head and the body, in order to include the entire length of the bolt body in the testing circuit.

Figure 4 shows the bolt of Figure l in posi-V tion between two sheets or plates 4i! and 4i The head is seated in a threaded sleeve 42 having a spherical socket 43 for receiving the head of the bolt. The lower part of the sleeve threads into plate 46 and the upper part of the sleeve supports a cap screw 44 for closing the socket chamber of the sleeve 42. In order to prevent engagement between the upper section lI of the head and the surface of the socket of sleeve 42, due to adjustments of the head in thef socket, the insulating layer 23 is preferably disposed to cover the adjacent surface of the upper section I'I or the upper section I1 may be cut back slightf ly for a short distance back from the circle of contact between thetwo sections.

The lower end or tip 46 of the bolt body is peened over on sheet 4I to secure the bolt in place. The tip of the bolt and the end of the core rod I5 may now be utilized'as terminals to connect the bolt body into an electric test circuit, as shown in Figure 3 to be tested.V By means of this construction, a test of each bolt may be easily and quickly made without necessitating cleaning out the central passage as required by present practice, since contact with the head end is available through the core rod I5.

A plug 48 may be inserted in the end of the bolt to cover the end of the rod. When thebolt is to be tested, the plug is removed.

Two general types of flexible staybolts are in use at present.Y One type consists of a bolt with an integral enlarged head of the same material as the body of the bolt. The other type of bolt consists of a bolt body having a separate head,Y

said head having its inner surface threaded and screwed o-nto the bolt body and being secured tothe end ofl the bolt by welding, peening or other suitable method. A staybolt is subjected to such transverse and vibratory stresses that a ductible and elastic metal is required to withstand these stresses as well as the ordinary tensile stress to which the bolt is subjected when the boiler is in service.

The bearing surface vof the bolt head is subjected to a great deal of friction as it moves in its seat, and, unless the metal of bolt head can withstand this Wearing satisfactorily, it will sometimes freeze or adhere to the metal formingv the seat in which the bolt head rests, thereby locking and eventually breaking the bolt. f

If a separate head is screwed onto the body Yo the bolt as hereinbefore described, the cutting CII of the threads in the bolt into the separate head weaken the latter to such an extent that breakage of the separate head often occurs.

The bolts and the assembly structures embodying the principles of my invention have the two characteristics required, namely, ductility and a satisfactory wearing surface, by using a bearing ring as the seating vsection of the head of the bolt and making it of a material that will satisfactorily withstand friction; have suicient strength to prevent breakage during service and be adapted to fit under the head of the bolt in such a manner as to lose none of its strength and give a smooth wearing surface to fit into the seat in which it rests, and by using a material for the body of the bolt that gives ductility and strength. The seat for the bearing ring may be in the boiler sheet with an opening for the bolt, as will be described hereinafter with reference to Figures and 6, or the seat may be in a sleeve secured to the boiler sheet, as shown in Figures 3 and 4.

In Figure 3, the bearing ring 33 is not considered as a part of the bolt head, but rather as an independent seating element. In Figure 4, however, the lower section I 8 of the head is considered as a part of the head although it is not an integral part. In that modification, the outer surface of the lower section is part of a spherical surface. For appearance, the outer surface of the top section I1 is a part of a spherical surface. In Figure 3 the under surface of the bolt head, where it engages the bearing ring 33, is preferably spherical to provide maximum case of flexing of the bolt.

In Figures 5 and 6 are illustrated further modications embodying various features of my invention.

In Figure 5 the bolt 50 is seated with its lower head-section 5I directly in a recess in the outer sheet or plate 40. The lower head section 5I is insulated from the main head section and serves as the bearing ring which adjusts itself in the boiler sheet or plate 40. A cap 54 is provided to cover the head of the bolt and has its inner surface 55 insulated. The cap is secured to the boiler sheet 40. V

In Figure 6, the other bolt modification is shown, with which a bearing ring 60 is provided, seated in and insulated from the boiler sheet 40 by a suitable insulating lmedium 6|. A cap 62 covers the head of the bolt and is secured to the boiler sheet 40. 'I'he inner surface of cap, 63, is insulated. I reserve the right to use a cap in assembles Figures 5 and 6 without an insulated inner surface.

In Figure 7 is shown a modification similar to that in Figure 3 except that the sleeve 10 and the bearing ring 1| have outer surfaces of coneshape to provide a tight seating iit. 'Ihe bearing ring is insulated from the sleeve by an insulating medium 12.

This principle of using a bearing ring of satisfactory and proper bearing metal may be utilized for solid bolts, as in Figure 7, as well as for hollow bolts of the tell-tale type, since vthe advantage of a proper bearing surface may be utilized independently of the testing advantage.

My invention is not limited therefore to any of the specific structural details, since they may be variously modified without departing from the spirit and scope of the invention as set forth in the appended claims.

I claim as my invention:

1. A staybolt comprising a head, a hollow bolt body and an electrical conducting element disposed in, and extending the length of, the hollow body and electrically insulated from the body along its length but electrically connected to the body at the head end of the hollow passage, said conducting element being of suicient self-sustaining character and strength to be unaffected by fracture of the bolt body or by the resultant leakage, and serving to permit an electrical test of the bolt structure under all operating conditions.

2. A staybolt comprising a head and a hollow body integral therewith, and means electrically connected to the head end of the hollow body and integral therewith but insulated from the body throughout its length, said means being of suiiicient self-sustaining character and stability to be unaffected by leakage resulting from fracture of 'the bolt body and serving to permit an electrical connection to be readily made to the head end of the bolt under all operating conditions of the bolt.

3. A staybolt comprising a head, a hollow bolt body, and an electrical conductor connected permanently to the head end of the bolt body and extending to the tip of the bolt body and insulated from the bolt body, said conductor being of sufficient self-sustaining character and stability to be unaifected by leakage resulting from fracture of the bolt body, and serving to be available for electrical testing of the bolt under all operating conditions while it is in position.

4. A staybolt structure comprising a bolt having an enlarged head, a bearing ring on the bolt and adapted to iit against the under surface of the head, the outer surface of the bearing ring constituting a section of a sphere, to permit the bolt and the ring to move freely to enable the bolt head to adjust its position, as necessary, in an assembled structure, and a permanent electrical insulating medium between the head and the bearing ring.

5. A staybolt comprising a bolt having an enlarged head, a seat for the head having its outer surface constituting a section of a sphere and an electrical insulating medium between the seat and the head, to permit the bolt and the seat to move freely to enable the bolt head to adjust its position, as necessary, in an assembled structure.

6. A staybolt for use between two sheets of a boiler structure, comprising a hollow bolt having an enlarged head, a conducting core extending the full length of the hollow bolt and electrically joined thereto at the head end but insulated along its length, whereby both ends of the bolt body may be connected in an electrical circuit for testing the conductivity and condition of the bolt, and a bearing ring on the bolt and fitting against the under side of the head but electrically insulated therefrom by a suitable insulating medium whereby the head of the bolt may be insulated from the sheet when the bolt is secured in position.

7. A staybolt structure comprising a staybolt with a tell-tale hole extending from one end of the bolt into but not through the head of the bolt, and means for electrically insulating the head of the bolt from the boiler sheet, under normal operating conditions, to permit electrical testing of the bolt as a unit without current leakage to the boiler sheet from the head end of the bolt.

8. A staybolt for use between two sheets of boiler structure, comprising a hollow bolt having an enlarged head, a conducting core extending the full length of the hollow bolt and electrical- 1y joined thereto at its head end but insulated along its length, whereby both ends of the bolt body may be connected in an electrical circuit for testing the conductivity and condition of the bolt, and a bearing ring on the bolt and fitting against the underside of the head but electrically insulated therefrom by a permanent insulating medium whereby the head of the bolt may be insulated from the sheet when the bolt is secured in position, and a removable plug in the tip or re sheet end of the bolt.

9. A staybolt structure comprising a staybolt with a head and hollow bolt body integral therewith and electrical conducting core joined to the bolt body at its head end :iut insulated from the bolt body along its length, a sleeve secured to the boiler sheet,` a permanent electrical insulating medium between the head of the bolt and the sleeve, and a closure over the head of the bolt.

10. In a staybolt structure, the combination with a boiler sheet provided with an opening for the head of a staybolt, of a staybolt comprising a head, a hollow bolt body integraitherewith and a permanent electrical conducting core joined to the bolt body at its head end but insulated from the bolt body along its length, an insulating mediurn between the head of the bolt and the boiler sheet, and a closure over the bolt head and secured to the sheet= 11. A staybolt structure comprising a staybolt with an enlarged head, a hollow bolt body integral therewith and an electrical conducting core joined to the bolt cody at its head end but insulated from the ybolt body along its length, a bearingV ring on the bolt and adapted to fit under the head, one surface of the bearing ring constituting a section of a sphere, a permanent electrical insulating medium between the bearing ring and the boiler sheet, a boiler sheet provided with an opening for the head of the bolt and a closure over the bolt head and secured to the boiler sheet, 'the closure having the inner surface electrically insulated.

l2. A staybolt structure comprising a staybolt with an enlarged head, a hollow bolt body integral therewith and a conducting core joined to the bolt body at its head end but electrically insulated from the bolt body along its length, a bearing ring cn the bolt and adapted to t under the head, one surface of the bearing ring constituting a section of a sphere, an electrical insulating medium between the bearing ring and the sleeve, a' sleeve secured to the bc-iler sheet and a closure overthe bolt head.

13. The method of assembling a staybolt structure for a boiler, which consists in installing the staybolts with their head ends permanently insulated from the boiler sheet, whereby any bolt body may be electrically tested without diversion of testing current from the bolt being tested.

14. The method of testing staybolts in a staybolt structure, which consists in insulating the head of the bolt from an associated metal sheet, and applying electrical testing potential to both ends of the body of a staybolt being tested.

RALPH w. FRIDAY. 

